The objective of this conference is to utilize linkage analysis to define the genetic basis of those human leukodystrophies that are as yet undefined. Recent experience highlights the need for this approach as well as its potential. While the genetic basis of 8 of the leukodystrophies has been defined during the last 10 years, and non- invasive diagnostic as says are available for each, diagnosis remains unclear in at least half of the patients in whom a leukodystrophy is suspected on the basis of magnetic resonance imaging and clinical studies. Multidisciplinary study of these patients has identified at least 3 groups in which clinical, radiological and pedigree patterns are sufficiently homogeneous to suggest that they represent distinct entities that have the potential of being defined by linkage analysis. The United. Leukodystrophy Foundation (ULF) now proposes a conference that will bring together geneticists, neuroscientists, cell biologists, clinicians, radiologists and veterinarians to plan a coordinated series of studies to determine the basis of undefined leukodystrophies by linkage analysis. The ULF, now in its 16th year, is in a strong position to facilitate this effort since it has sponsored a series of successful annual conferences that have increased in size and scope each year, that have brought together scientists and clinicians with families who wish to support and participate in this research.